Eur. Phys. J. D 25, 31-40 (2003)
https://doi.org/10.1140/epjd/e2003-00216-4

Photodissociation and photoionization of sodium coated C₆₀ clusters

¹ Laboratoire de Spectrométrie Ionique et Moléculaire (UMR 5579 du CNRS) , 43 boulevard du 11 novembre 1918, 69622 Villeurbanne Cedex, France
² Laboratoire de Physique de la Matière Condensée et Nanostructures (UMR 5586 du CNRS) , 43 boulevard du 11 novembre 1918, 69622 Villeurbanne Cedex, France

Corresponding author: ^a pellarin@lasim.univ-lyon1.fr

Received: 3 March 2003
Revised: 7 May 2003
Published online: 17 July 2003

Abstract

(C₆₀)_mNa_n clusters are produced in a tandem laser vaporization source and analyzed by photoionization and photofragmentation time-of-flight mass spectroscopy. At low sodium coverage, the special behavior of (C₆₀)Na_n clusters is consistent with a significant electron transfer from the first six adsorbed atoms towards each of the C₆₀ fullerenes and an ionic-like bonding in this size range. However, the stability of the (C₆₀)Na cation is found much more pronounced than the one of (C₆₀)Na predicted to be a magic size under the hypothesis of a full charge transfer from the metal atoms to the C₆₀ molecule. When more sodium atoms are present, metal-metal bonds tend to become preponderant and control the cluster properties. Relative to the number of sodium atoms, an odd-even alternation in their stability is explained by the high dissociation rates for even-numbered clusters. The even clusters evaporate neutral sodium atoms whereas odd ones prefer to evaporate Na₂ molecules. The hypotheses for the growth of a sodium droplet that does not wet the fullerene surface or for the formation of a concentric metallic layer are discussed in the light of this study.